Foam materials have been coated on or spread on various types of sheet materials, for example, as wear layers or facings, or as cushioning layers or backings, in the manufacture of floor coverings, such as carpets and rugs, or other articles, such as desk, table, or counter tops, wall coverings, book covers, decorative containers, fabrics for use as upholstery, clothing, and automotive interiors, etc.
In such coating or spreading operations, it is normally desired that substantial uniformity of the amount and the thickness of the coating be obtained and that the final foam layer be relatively free of undesirable air bubbles, blisters, or blotches, in the form of large or irregular spots or blemishes, which would seriously detract from the appearance and the properties of the final product and unfortunately reduce its commercial acceptability. Such objectionable features of non-uniformity and undesirable air bubbles, blisters, and blotches, in the form of large or irregular spots or blemishes, were all the more pronounced in the spreading or coating of foam materials on relatively wide sheets of material. In such an operation, a traversing supply mechanism was usually employed to accumulate a pile or mass of foam material in a reciprocating back-and-forth motion behind a relatively wide doctor bar, roll, or blade, in order to accomodate the relatively wide width of the sheet material. The reciprocating back-and-forth motion appeared to increase the non-uniformity and the number of the undesirable air bubbles, blisters, and blotches in the final foam product.